The inspection of surfaces of components for turbine engines forms an important part of the overall quality which ensures the reliability of the engine. There are numerous nondestructive evaluation systems which measure surface texture parameters, examine surface defects, and detect surface flaws such as nicks, dents, tears, cracks, etc. These systems transmit some form of energy into or through the workpiece and observe the manner in which the workpiece and energy inter-react. The systems most commonly employed involve ultrasonic magnetic, eddy current or infrared energy. These systems however are not well suited for a workpiece having a large area with a relatively complex configuration such as a jet engine turbine blade.
In these workpieces where the surface are accessible only by the application of a fluorescent penetrant, fluorescent penetrant inspection is well suited to the examination of the workpiece surface. This invention relates to fluorescent penetrant inspection which is used extensively for detection of surface connected discontinuities in relatively complex structural workpieces.
In current fluorescent penetrant inspection practice, an inspector examines a workpiece in which a fluorescent penetrant has been applied to the surface. The penetrant seeps into any surface defects of the workpiece. The workpiece is washed and dryed leaving only penetrant in the defects. The inspector takes the fluorescent penetrant processed workpiece into a darkened room, waits for his eyes to adapt to the darkness and examines the workpiece under ultraviolet light. The ultraviolet light excites the dye in any penetrant in a surface defect causing emission of a visual greenish yellow light. An area emitting this light is typically indicative of a surface defect. The inspector measures the indicated area with a width gauge, or similar device, to assess the size of the area and determine the workpiece's acceptability or rejectability.
One of the problems with this type of inspection is the dependency upon the accuracy of a human inspector to detect a surface defect and to assess the size of the defect. The current manual methods of inspection are labor intensive, slow and subject to human limitations. Because of these problems it is desirable to have a system which is not limited by human response for detecting and measuring surface defects.